Ink jet printing process

ABSTRACT

An ink jet printing process for improving the ozone stability of an ink jet image comprising:  
     a) providing an ink jet recording element comprising a support having thereon a porous image-receiving layer having interconnecting voids; and  
     b) applying droplets of a liquid ink on the image-receiving layer in an image-wise manner, the ink comprising water, humectant and a metallized, phthalocyanine dye, the metallized, phthalocyanine dye comprising the formula: 
     MPc(SO 3 X) a (SO 2 NRR′) b   
     wherein  
     M represents a metal;  
     Pc represents a phthalocyanine nucleus;  
     X represents hydrogen, alkali metal or an organic cation;  
     a is from 0 to 2;  
     R represents hydrogen; a substituted or unsubstituted alkyl group having from about 1 to about 15 carbon atoms, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group;  
     R′ represents a substituted or unsubstituted alkyl group having from about 1 to about 15 carbon atoms containing a hydroxy group, a substituted or unsubstituted aryl group containing a hydroxy group or a substituted or unsubstituted heterocyclic group containing a hydroxy group; and  
     b is from 1 to 4, with the proviso that a+b is an average of from 3 to 4.

CROSS REFERENCE TO RELATED APPLICATION

[0001] Reference is made to commonly assigned, co-pending U.S. patentapplication Ser. No. ______ by Andrievsky et al., filed concurrentlyherewith (Docket 81981) entitled “Ink Jet Printing Process”.

FIELD OF THE INVENTION

[0002] This invention relates to an ink jet printing process forimproving the ozone stability of an inkjet image.

BACKGROUND OF THE INVENTION

[0003] Ink jet printing is a non-impact method for producing images bythe deposition of ink droplets in a pixel-by-pixel manner to animage-recording element in response to digital signals. There arevarious methods which may be utilized to control the deposition of inkdroplets on the image-recording element to yield the desired image. Inone process, known as continuous ink jet, a continuous stream ofdroplets is charged and deflected in an imagewise manner onto thesurface of the image-recording element, while unimaged droplets arecaught and returned to an ink sump. In another process, known asdrop-on-demand inkjet, individual ink droplets are projected as neededonto the image-recording element to form the desired image. Commonmethods of controlling the projection of ink droplets in drop-on-demandprinting include piezoelectric transducers and thermal bubble formation.Ink jet printers have found broad applications across markets rangingfrom industrial labeling to short run printing to desktop document andpictorial imaging.

[0004] The inks used in the various ink jet printers can be classifiedas either dye-based or pigment-based. A dye is a colorant which ismolecularly dispersed or solvated by a carrier medium. The carriermedium can be a liquid or a solid at room temperature. A commonly usedcarrier medium is water or a mixture of water and organic co-solvents.Each individual dye molecule is surrounded by molecules of the carriermedium. In dye-based inks, no particles are observable under themicroscope. Although there have been many recent advances in the art ofdye-based ink jet inks, such inks still suffer from deficiencies such aslow optical densities on plain paper and poor light-fastness. When wateris used as the carrier medium, such inks also generally suffer from poorwater-fastness.

[0005] The ink jet receiving elements that can be used with the abovementioned inks must meet several requirements including producing highdensity images that will not smear, bleed or wander when exposed towater for short periods of time.

[0006] U.S. Pat. Nos. 4,632,703, 6,149,722 and 6,015,896, WO 00/08103and WO 98/49239 relate to inks containing phthalocyanine dyes used inink jet printing. However, there is no disclosure in these referencesthat these inks would be useful with a recording element containing aporous image-receiving layer.

[0007] It is an object of this invention to provide an inkjet printingprocess for improving the ozone stability of an ink jet image.

SUMMARY OF THE INVENTION

[0008] These and other objects are achieved in accordance with thepresent invention which comprises an ink jet printing process forimproving the ozone stability of an ink jet image comprising:

[0009] a) providing an ink jet recording element comprising a supporthaving thereon a porous image-receiving layer having interconnectingvoids; and

[0010] b) applying droplets of a liquid ink on the image-receiving layerin an image-wise manner, the ink comprising water, humectant and ametallized, phthalocyanine dye, the metallized, phthalocyanine dyecomprising the formula:

MPc(SO₃X)_(a)(SO₂NRR′)_(b)

[0011] wherein

[0012] M represents a metal;

[0013] Pc represents a phthalocyanine nucleus;

[0014] X represents hydrogen, alkali metal or an organic cation;

[0015] a is from 0 to 2;

[0016] R represents hydrogen; a substituted or unsubstituted alkyl grouphaving from about 1 to about 15 carbon atoms, a substituted orunsubstituted aryl group, or a substituted or unsubstituted heterocyclicgroup;

[0017] R′ represents a substituted or unsubstituted alkyl group havingfrom about 1 to about 15 carbon atoms containing a hydroxy group, asubstituted or unsubstituted aryl group containing a hydroxy group or asubstituted or unsubstituted heterocyclic group containing a hydroxygroup; and

[0018] b is from 1 to 4, with the proviso that a+b is an average of from3 to 4.

[0019] It was found that the ozone stability of an ink jet image wasimproved using the compounds described herein.

DETAILED DESCRIPTION OF THE INVENTION

[0020] In a preferred embodiment of the invention, the metallized,phthalocyanine dyes which may be used include the following: TABLE 1MPc(SO₃X)_(a)(SO₂NHR′)_(b) (M is Cu, and X, Pc, a and b being defined asabove) Dye R′ 1

2

3

4 —CH₂CH₂OH

[0021] (R═R′═—CH₂CH₂OH, and X, Pc, a and b being defined as above) TABLE2 Dye M 5 Cu 6 Ni

[0022] In another preferred embodiment of the invention, R represents asubstituted or unsubstituted alkyl group having from about 1 to about 15carbon atoms containing a hydroxy group, an aryl group containing ahydroxy group or a heterocyclic substituent containing a hydroxy group.

[0023] The dyes described above may be employed in any amount effectivefor the intended purpose. In general, good results have been obtainedwhen the dye is present in an amount of from about 0.2 to about 5% byweight of the ink jet ink composition, preferably from about 0.3 toabout 3% by weight. Dye mixtures may also be used.

[0024] The support for the ink jet recording element used in theinvention can be any of those usually used for ink jet receivers, suchas paper, resin-coated paper, plastics such as a polyester-type resinsuch as poly(ethylene terephthalate), polycarbonate resins, polysulfoneresins, methacrylic resins, cellophane, acetate plastics, cellulosediacetate, cellulose triacetate, vinyl chloride resins, poly(ethylenenaphthalate), polyester diacetate, various glass materials, andmicroporous materials such as microvoided polyester described incopending U.S. Ser. No. 09/656,129, filed Aug. 29, 2000, polyethylenepolymer-containing material sold by PPG Industries, Inc., Pittsburgh,Pa. under the trade name of Teslin®, Tyvek® synthetic paper (DuPontCorp.), and OPPalyte® films (Mobil Chemical Co.) and other compositefilms listed in U.S. Pat. No. 5,244,861. The thickness of the supportemployed in the invention can be, for example, from about 12 to about500 μm, preferably from about 75 to about 300 μm.

[0025] Antioxidants, antistatic agents, plasticizers and other knownadditives may be incorporated into the support, if desired. In apreferred embodiment, paper is employed.

[0026] In a preferred embodiment of the invention the porousink-receptive layer contains inorganic particles such as silica,alumina, titanium dioxide, clay, calcium carbonate, barium sulfate, orzinc oxide. In another preferred embodiment, the porous ink-receptivelayer comprises from about 30% to about 95% inorganic particles and fromabout 5% to about 70% polymeric binder, such as gelatin, poly(vinylalcohol), poly(vinyl pyrrolidinone) or poly(vinyl acetate). The porousink-receptive layer can also contain organic beads or polymericmicro-porous structures without inorganic filler particles as shown inU.S. Pat. Nos. 5,374,475 and 4,954,395, the disclosures of which arehereby incorporated by reference.

[0027] Examples of binders which may be used in the image-receivinglayer include polyvinyl alcohol, polyvinyl pyrrolidone, poly(ethyloxazoline), non-deionized or deionized Type IV bone gelatin, acidprocessed ossein gelatin or pig skin gelatin. The hydrophilic polymermay be present in an amount of from about 0.4 to about 30 g/m²,preferably from about 1 to about 16 g/m².

[0028] The pH of the aqueous ink compositions of the invention may beadjusted by the addition of organic or inorganic acids or bases. Usefulinks may have a preferred pH of from about 2 to 7, depending upon thetype of dye being used. Typical inorganic acids include hydrochloric,phosphoric and sulfuric acids. Typical organic acids includemethanesulfonic, acetic and lactic acids. Typical inorganic basesinclude alkali metal hydroxides and carbonates. Typical organic basesinclude ammonia, triethanolamine and tetramethylethylenediamine.

[0029] A humectant is employed in the ink jet composition of theinvention to help prevent the ink from drying out or crusting in theorifices of the printhead. Examples of humectants which can be usedinclude polyhydric alcohols, such as ethylene glycol, diethylene glycol,triethylene glycol, propylene glycol, tetraethylene glycol, polyethyleneglycol, glycerol, 2-methyl-2,4-pentanediol 1,2,6-hexanetriol andthioglycol; lower alkyl mono- or di-ethers derived from alkyleneglycols, such as ethylene glycol mono-methyl or mono-ethyl ether,diethylene glycol mono-methyl or mono-ethyl ether, propylene glycolmono-methyl or mono-ethyl ether, triethylene glycol mono-methyl ormono-ethyl ether, diethylene glycol di-methyl or di-ethyl ether, anddiethylene glycol monobutylether; nitrogen-containing cyclic compounds,such as pyrrolidone, N-methyl-2-pyrrolidone, and1,3-dimethyl-2-imidazolidinone; and sulfur-containing compounds such asdimethyl sulfoxide and tetramethylene sulfone. A preferred humectant forthe composition of the invention is diethylene glycol, glycerol, ordiethylene glycol monobutylether.

[0030] Water-miscible organic solvents may also be added to the aqueousink of the invention to help the ink penetrate the receiving substrate,especially when the substrate is a highly sized paper. Examples of suchsolvents include alcohols, such as methyl alcohol, ethyl alcohol,n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol,t-butyl alcohol, iso-butyl alcohol, furfuryl alcohol, andtetrahydroftrfuryl alcohol; ketones or ketoalcohols such as acetone,methyl ethyl ketone and diacetone alcohol; ethers, such astetrahydrofuran and dioxane; and esters, such as, ethyl lactate,ethylene carbonate and propylene carbonate.

[0031] Surfactants may be added to adjust the surface tension of the inkto an appropriate level. The surfactants may be anionic, cationic,amphoteric or nonionic. A preferred surfactant for the ink compositionof the present invention is Surfynolt 465 (Air Products) at a finalconcentration of 0.1% to 1.0%.

[0032] A biocide may be added to the composition of the invention tosuppress the growth of micro-organisms such as molds, fungi, etc. inaqueous inks. A preferred biocide for the ink composition of the presentinvention is Proxelt GXL (Zeneca Specialties Co.) at a finalconcentration of 0.05-0.5 wt. %.

[0033] A typical ink composition of the invention may comprise, forexample, the following substituents by weight: colorant (0.2-5%), water(20-95%), humectant (5-70%), water miscible co-solvents (2-20%),surfactant (0.1-10%), biocide (0.05-5%) and pH control agents (0.1-10%).

[0034] Additional additives which may optionally be present in the inkjet ink composition of the invention include thickeners, conductivityenhancing agents, anti-kogation agents, drying agents, and defoamers.

[0035] The image-recording layer used in the process of the presentinvention can also contain various known additives, including mattingagents such as titanium dioxide, zinc oxide, silica and polymeric beadssuch as crosslinked poly(methyl methacrylate) or polystyrene beads forthe purposes of contributing to the non-blocking characteristics and tocontrol the smudge resistance thereof; surfactants such as non-ionic,hydrocarbon or fluorocarbon surfactants or cationic surfactants, such asquaternary ammonium salts; fluorescent dyes; pH controllers;anti-foaming agents; lubricants; preservatives; viscosity modifiers;dye-fixing agents; waterproofing agents; dispersing agents; UV-absorbingagents; mildew-proofing agents; mordants; antistatic agents,anti-oxidants, optical brighteners, and the like. A hardener may also beadded to the ink-receiving layer if desired.

[0036] In order to improve the adhesion of the image-recording layer tothe support, the surface of the support may be subjected to a treatmentsuch as a corona-discharge-treatment prior to applying theimage-recording layer.

[0037] In addition, a subbing layer, such as a layer formed from ahalogenated phenol or a partially hydrolyzed vinyl chloride-vinylacetate copolymer can be applied to the surface of the support toincrease adhesion of the image recording layer. If a subbing layer isused, it should have a thickness (i.e., a dry coat thickness) of lessthan about 2 μm.

[0038] The image-recording layer may be present in any amount which iseffective for the intended purpose. In general, good results areobtained when it is present in an amount of from about 2 to about 46g/m², preferably from about 6 to about 16 g/m², which corresponds to adry thickness of about 2 to about 42 μm, preferably about 6 to about 15μm.

[0039] The following examples are provided to illustrate the invention.

EXAMPLES

[0040] Synthesis of Compound 2

[0041] Compound 2 as illustrated above was prepared as follows: Copperphthalocyanine (14 g) was added to chlorosulfonic acid (125 g) over 45minutes, while keeping the temperature below 40° C. The mixture was thenheated to 140-150° C. and stirred for 5 hours. After cooling to roomtemperature, thionyl chloride (49 g) was added dropwise over 30 minutes,and the mixture kept at 80 ° C. for 3 hrs. After cooling to roomtemperature, the mixture was poured on ice and stirred vigorously, whilekeeping the temperature below 5° C. Precipitate was filtered off, washedextensively with water at 5° C., and used in the next step.N,N-Bis(hydroxyethyl)trimethylene diamine (27 g) and sodium carbonate(15 g) were dissolved in 500 mL water at 5° C. Wet phthalocyanine filtercake was added all at once, and the reaction mixture warmed to roomtemperature, and then heated at 50° C. overnight. Ethanol (1.5 L) wasadded, and mostly inorganic material was filtered off. Liqueurs wereconcentrated, and the product precipitated with acetone, filtered off,washed with ethanol, and dried to yield compound 2. The other compoundsin Table 1 and nickel analogs were prepared in a similar manner.

Example 1 Cu Phthalocyanine Dye

[0042] Recording Element 1

[0043] A coating solution for a base layer was prepared by combiningfumed alumina (Cab-O-Sperse® PG003, Cabot Corp.), poly(vinyl alcohol)(Gohsenol® GH-23A, Nippon Gohsei Co., Ltd.) and2,3-dihydroxy-1,4-dioxane (Clariant Corp.) in a ratio of 88:10:2 to givean aqueous coating formulation of 30% solids by weight.

[0044] A coating solution for an image-receiving layer was prepared bycombining fumed alumina (Cab-O-Sperse® PG003, Cabot Corp.), poly(vinylalcohol) (Gohsenol(® GH-23A, Nippon Gohsei Co.) and Polymer A in a ratioof 85:3:12 to give an aqueous coating formulation of 10% solids byweight. The fumed alumina particles have a primary particle size of fromabout 7 to about 40 nm in diameter and are aggregated up to about 150mn. Surfactants Zonyl® FSN (E. I. du Pont de Nemours and Co.) and Olin®10 G (Dixie Chemical Co.) were added in small amounts as coating aids.

[0045] The above coating solutions were simultaneously bead-coated at40° C. on polyethylene-coated paper base which had been previouslysubjected to corona discharge treatment. The image-receiving layer wascoated on top of the base layer. The coating was then dried at 60° C. byforced air to yield a two-layer recording element in which thethicknesses of the bottom and topmost layers were 40 μm (43 g/m²) and 2μm (2.2 g/m²), respectively.

[0046] Recording Element 2

[0047] The following commercially-available receiving element with aporous image-receiving layer was used: Konica Photo Quality Ink JetPaper QP, No: KJP-LT-GH-15-QP PI.

[0048] Preparation of Invention Inks

[0049] Inks containing the dyes employed in the invention as illustratedabove and identified in Table 3 were prepared with de-ionized watercontaining humectants of diethylene glycol and glycerol, each at 6%, abiocide, Proxel® GXL at 0.003 wt % and a surfactant, Surfynol® 465 (AirProducts Co.) at 0.5 wt. %. The dye concentrations were based onsolution absorption spectra and chosen such that the final ink whendiluted 1:1000, would yield a transmission optical density ofapproximately 1.0.

[0050] Preparation of Control Inks

[0051] These inks were prepared the same as the Invention Inks exceptthat the following control dyes were used which are metallizedphthalocyanine dyes but which have different substitutes than those setforth in the invention: C-1 Direct Blue 199 C-2CuPc(SO₃Na)_(a)(SO₂NH(CH₂)₃SO₃Na)_(b) C-3 CuPc(SO₃Na)_(c); c is from 2to 4. (Pc and a are defined as above in the formula)

[0052] Printing of Test Images

[0053] The above prepared inks were filtered through a 0.45 μmpolytetrafluoroethylene filter and placed into an empty Lexmark inkcartridge, No: Lexmak 15MO120, and fitted into the ink station of aLexmark Z-51 printer. A test image consisting of 4 variable densitypatches approximately 10 by 10 mm in size, and ranging from 25% dotcoverage to 100% dot coverage was printed on to the following receivingelements: Element 1 above and Konica Photo Quality Ink Jet Paper QP, No:KJP-LT-GH-15-QP PI.

[0054] Evaluation of Test Images

[0055] For each ink, the Status A red reflection densities of the abovedescribed patches corresponding to 75% and 100% dot coverage weremeasured using an X-Rite 820 densitometer. The red density at 100% dotcoverage (d-max) is listed in the Table 2 below. The stepped images werethen placed in a dark chamber containing air and ozone gas at 5 ppm at50% RH for 3 days. The Status A densities of the stepped images werere-measured and the retained dye % in Status A red density for the 75%dot coverage patches were calculated for each ink and are also listed inthe following Table 2. A % retained value of greater than about 45% isconsidered to be acceptable. TABLE 3 Ozone Fade % Retained InkContaining Dye Recording Element 1 Recording Element 2 1 93 87 2 94 82 380 NA 4 92 NA 5 93 84 C-1 24 23 C-2 20 18 C-3 20 19

[0056] The above results show that the combination of the metallizedphthalocyanine dyes as described in the invention with a porousimage-receiving layer produced less fade than the control dyes in theozone test.

Example 2 Ni Phthalocyanine Dye

[0057] Preparation of Invention Ink

[0058] An ink was prepared similar to the invention inks in Example 1above, except that it contained dye 6.

[0059] Preparation of Control Ink

[0060] This ink was prepared the same as the above Invention Inks exceptthat the following control dye was used which has different substitutesthan those set forth in the invention:

[0061] C-4 Nickel (II) phthalocyaninetetrasulfonic acid, tetrasodiumsalt (Aldrich Chemical Co.)

[0062] Printing of Test Images and Evaluation

[0063] The above prepared inks were printed and evaluated as in Example1 with only Recording Element 1. The following results were obtained:TABLE 4 Ink Containing Dye Ozone Fade % Retained 6 100 C-4  44

[0064] The above results show that the combination of the metallizedphthalocyanine dyes as described in the invention with a porousimage-receiving layer had no fade as compared to the control dye in theozone test.

[0065] Although the invention has been described in detail withreference to certain preferred embodiments for the purpose ofillustration, it is to be understood that variations and modificationscan be made by those skilled in the art without departing from thespirit and scope of the invention.

What is claimed is:
 1. An ink jet printing process for improving theozone stability of an ink jet image comprising: a) providing an ink jetrecording element comprising a support having thereon a porousimage-receiving layer having interconnecting voids; and b) applyingdroplets of a liquid ink on said image-receiving layer in an image-wisemanner, said ink comprising water, humectant and a metallized,phthalocyanine dye, said metallized, phthalocyanine dye comprising theformula: MPc(SO₃X)_(a)(SO₂NRR′)_(b) wherein M represents a metal; Pcrepresents a phthalocyanine nucleus; X represents hydrogen, alkali metalor an organic cation; a is from 0 to 2; R represents hydrogen; asubstituted or unsubstituted alkyl group having from about 1 to about 15carbon atoms, a substituted or unsubstituted aryl group, or asubstituted or unsubstituted heterocyclic group; R′ represents asubstituted or unsubstituted alkyl group having from about 1 to about 15carbon atoms containing a hydroxy group, a substituted or unsubstitutedaryl group containing a hydroxy group or a substituted or unsubstitutedheterocyclic group containing a hydroxy group; and b is from 1 to 4,with the proviso that a+b is an average of from 3 to
 4. 2. The processof claim 1 wherein said porous image-receiving layer havinginterconnecting voids comprises organic or inorganic particulatematerials in a polymeric binder.
 3. The method of claim 2 wherein saidinorganic particles comprise silica, alumina, titanium dioxide, clay,calcium carbonate, barium sulfate, or zinc oxide.
 4. The method of claim1 wherein said porous image-receiving layer comprises from about 10% toabout 95% inorganic particles and from about 5% to about 90% of apolymeric binder.
 5. The method of claim 4 wherein said polymeric binderis gelatin, poly(vinyl alcohol), poly(vinyl pyrrolidinone) or poly(vinylacetate).
 6. The process of claim 1 wherein said R represents hydrogen.7. The process of claim 1 wherein said R′ represents


8. The process of claim 1 wherein M represents copper, nickel, aluminum,zinc, iron, or cobalt.
 9. The process of claim 1 wherein R represents asubstituted or unsubstituted alkyl group having from about 1 to about 15carbon atoms containing a hydroxy group, an aryl group containing ahydroxy group or a heterocyclic substituent containing a hydroxy group.10. The process of claim 1 wherein M represent Cu or Ni, and each R andR′ represents —CH₂CH₂OH.